Shear-coupled grain boundary (GB), migration is an efficacious
plasticity mechanism in nanocrystalline materials. However, the
atomistic aspects of this kind of GB motion have received far less
attention in bcc metals than that in fcc ones. In this work, we have
investigated the shear-coupled migration (SCM) of Sigma 1310001 (5)
over bar) and Sigma 8510007 (6) over bar) GBs in bcc tungsten using
atomistic simulations. We demonstrate that the SCM of the two GBs
proceeds via the collective glide of GB dislocations along the < 100 >
and < 111 > directions, respectively. The magnitudes of the GB migration
depend on system lateral dimension, temperature and GB dislocation
character. Nudged elastic band calculations in combination with the
dynamic simulations give the elementary processes of the SCM and show
that the shear strength and thermal resistance of the < 100 > mode GB is
much higher than the < 111 > one, consistent with the fact that the <
100 > dislocations are much more difficult to glide than the 1/2 < 111 >
dislocations. This conclusion is further supported by the simulation
results of GB random walk behavior under the free boundary condition.
The present results demonstrate that the atomistic SCM process is
fundamentally related to the character of GB dislocations. (C) 2016
Elsevier B.V. All rights reserved.